Don't know if anyone will benefit from this, but I just picked one up for some extra xbox one storage. I think it was a bit cheaper at argos (eBay) last week but I missed out on that unfortunately so anyone that missed it might like this. This is currently the cheapest I could find that doesnt have a plug with it.
-2.5" External Hard Drive Interface
-USB 3.0 (USB 2.0 compatible)Max transfer rate ~ 5.0 GBPSPower
-USB bus power (max. 900 mA)